Ventricular premature beats (VPBs) will be studied in patients with coronary heart disease (CHD) and in subjects at high as well as low risk for CHD. Three broad lines of inquiry will be pursued: 1. Determination of optimal methods for VPB exposure. 2. Improved qualitative and quantitative categorization of VPBs as well as definition of the circumstances for their occurrence in relation to the presence of CHD or certain constellations of risk factors for CHD. 3. Development of new methods for testing antiarrhythmic drug efficacy as well as assessing coronary bypass as a method for VPB control. The methods for VPB detection to be employed will include programmed trendscription, 24-hour ambulatory monitoring and various forms of exercise stress testing.